A disc storage system includes a rotating disc and a transducer. The transducer is carried on a slider which is supported by an armature. The armature is used to move the slider radially across the disc surface whereby information may be read from or written to the disc surface of the transducer. The slider includes an air bearing surface which faces the disc surface. As the disc rotates, the air bearing surface causes the slider to "fly" over the disc surface. pads are provided on the air bearing surface to improve operational characteristics of the system and texturing is provided to a landing zone region on the disc surface.
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11. A method reducing stiction in a disc storage system, comprising:
texturing a landing zone region on a surface of a disc of the storage system; forming pads on rails of a slider; wherein the pads and texturing cooperate to reduce stiction in the landing zone region, the texturing further configured to cooperate with the pads to allow reduced height of the pads and reduced fly height the pads having a height to provide a desired maximum stiction during CSS; and forming pads proximate a trailing edge of the slider with a height which is less than a height of pads proximate a leading edge.
16. A disc drive storage system, comprising:
a rotating disc having a disc surface; a transducing head configured to read and write on the disc surface; transducing circuitry coupled to the transducing head; a slider having rails formed thereon and having an air bearing surface, the slider supporting the transducing head proximate the disc surface; a plurality of pads carried on the rails having an area which contact the disc surface during contact start/stop (CSS) and a height selected to provide a desired maximum stiction during CSS; and a landing zone region on the disc surface having texturing formed thereon, wherein the texturing has a spacing of 11×11 μm to 25×25 μm.
17. A disc drive storage system, comprising:
a rotating disc having a disc surface; a transducing head configured to read and write on the disc surface; transducing circuitry coupled to the transducing head; a slider having rails formed thereon and having an air bearing surface, the slider supporting the transducing head proximate the disc surface; a plurality of pads carried on the rails having an area which contact the disc surface during contact start/stop (CSS) and a height selected to provide a desired maximum stiction during CSS; and a landing zone region on the disc surface having texturing formed thereon, wherein the texturing has a diameter of 4 μm to 6 μm and the pads have a spacing of 60 μm to 80 μm center-to-center.
1. A disc drive storage system, comprising:
a rotating disc having a disc surface; a transducing head configured to read and write on the disc surface; transducing circuitry coupled to the transducing head; a slider having rails formed thereon and having an air bearing surface, the slider supporting the transducing head proximate the disc surface; a plurality of pads carried on the rails having an area which contact the disc surface during contact start/stop (CSS) and a height selected to provide a desired maximum stiction during CSS; and a landing zone region on the disc surface having texturing formed thereon; wherein the slider has a leading edge and a trailing edge and pads proximate the trailing edge have a height which is less than pads proximate the leading edge such that fly height of the trailing edge is reduced, the pads and texturing have respective heights to reduce stiction in the landing zone and the texturing having a height to cooperate with the pad height to allow reduced fly height of the slider.
5. The disc storage system of
8. The disc storage system of
9. The disc storage system of
10. The disc storage system of
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The present invention claims priority to Provisional Application Serial No. 60/151,105, filed Aug. 27, 1999; and application Ser. No. 09/029,276, filed Dec. 9, 1998.
The present invention relates to disc storage systems for storing information. More specifically, the present invention relates to sliders used in such systems.
Disc drives are used for storing information, typically as magnetically encoded data, and more recently as optically encoded data, on a disc surface. A transducing head is carried on a air-bearing slider that rides on a bearing of air above the disc surface as the disc rotates at high speed. In another technique, the slider contacts the disc surface with no air bearing interface such as is shown in U.S. Pat. Nos. 5,453,315 and 5,490,027. The head is then positioned radially over the disc to read back or write at a desired location. Benefits associated with an air bearing design are lost in such "contact" sliders.
In an air bearing design, the air bearing provides an interface between the slider and the disc which prevents damage to the disc over the life of the system, provides damping if the disc drive system undergoes shock due to external vibrations. The air bearing is also used to provide a desired spacing between the transducing element and the disc surface. A bias force is applied to the slider by a flexure armature in a direction toward the disc surface. This bias force is counteracted by lifting forces from the air bearing until an equilibrium is reached. The slider will contact the disc surface if the rotating speed of the disc is insufficient to cause the slider to "fly." This contact typically occurs during start up or shut down of the disc. If the slider contacts a region of the disc which carries data, the data may be lost and the disc permanently damaged.
In many disc drive systems, a lubricant is applied to the disc surface to reduce damage to the head and the disc surface during starting and stopping. Air or gas also acts as a lubricant. However, a phenomenon known as "stiction," which is caused by static friction and viscous shear forces, causes the slider to stick to the disc surface after periods of non use. The lubricant exacerbates the stiction problem. The stiction can damage the head or the disc when the slider is freed from the disc surface. Additionally, the spindle motor used to rotate the disc must provide sufficient torque to overcome the stiction.
One technique used to overcome the problem associated with stiction is to provide texturing to at least a portion of the disc surface. As the fly height of disc drive system has been continually reduced to produce smaller and smaller transducer spacing, mechanical interference is increased. This is especially true in discs which use a textured landing zone such as that provided by laser texture bumps. Such laser texturing is provided to reduce the high levels of stiction that are generated by the smooth surfaces of the head and disc when they contact. However, using present laser texturing technology, the required height of the bumps in the landing zone textured region require to mitigate the stiction is greater than the nominal flying height of the head. This causes excessive wear and interference in the landing zone region. However, if the texturing in the landing zone is reduced, the stiction quickly increases to unacceptable levels.
A disc storage system includes a rotating disc and a transducer. The transducer is carried on a slider which is supported by an armature. The armature is used to move the slider radially across the disc surface whereby information may be read from or written to the disc surface of the transducer. The disc surface includes a landing zone region which is textured, for example, through laser texturing techniques. The slider includes an air bearing surface which faces the disc surface. As the disc rotates, the air bearing surface causes the slider to "fly" over the disc surface. Pads are provided on the air bearing surface and cooperate with bumps or other texturing in the landing zone region to reduce stiction without damaging the slider.
During operation, drive controller 26 receives position information indicating a portion of disc 12 to be accessed. Drive controller 26 receives the position information from an operator, from a host computer, or from another suitable controller. Based on the position information, drive controller 26 provides a position signal to actuator 18. The position signal causes actuator 18 to pivot about axis 22. This, in turn, causes actuator 18 to pivot about axis 22. This, in turn, causes slider 36 (and consequently the transducer mounted on slider 36) to move radially over the surface of disc 12 in a generally arcuaic path indicated by arrow 38. Drive controller 26 and actuator 18 operate in a known closed loop, negative feedback manner so that the transducer carried by slider 36 is positioned over the desired portion of disc 12. Once the transducer is appropriately positioned, drive controller 26 then executes a desired read or write operation.
Recording density can be increased by reducing the fly height of slider 36. Close proximity of slider 36 with disc 12 allows greater accuracy in reading and writing information onto disc 12.
Stiction and fly/stiction are two major phenomena that impair the use of ultra-low flying recording heads to increase recording areal density. The solution to these problems has been to generate, in a controlled fashion, some asperities, or texture, on the media surface to reduce the area of contact at the head-media interface. The presence of these asperities on the media surface, although they can be confined to within a small dedicated zone 40 (i.e., a "landing zone"), enhances the chance of head-media contact during operation and thereby sets the limit to the true attainment of ultra-low flying. Using current laser texturing technology, the height of the bumps in the landing zone required to mitigate stiction is surpassing the nominal flying height of the head. This causes interference between the slider surface and the textured landing zone. This interference can result in increased head and media wear which will eventually lead to interface failure. If the size of the bumps in the textured region is reduced, the stiction quickly increases to unacceptable levels, ranging from 10 grams to as high as 50 grams or more, depending upon the amount of height reduction.
The present invention utilizes pads on the slider surface in conjunction with texturing of the landing zone region. With the present invention, the spacing required to mitigate stiction is shared between the slider and the disc. Examples of slider and pad configurations are described in U.S. patent application Ser. No. 09/029,276, filed Dec. 9, 1998 and entitled "SLIDER FOR DISC STORAGE SYSTEM" which is assigned to the present assignee and is incorporated herein by reference in its entirety.
The pads 46 also permit a higher level of interference between the slider 36 and the disc 12 because they are made of diamond-like carbon which has excellent wear properties. This wear occurs on pads 46 instead of on the slider 36 or on disc 12. If the height and placement of pads 46 is chosen appropriately, the wear will reach a steady state and stiction will remain at very low levels over the entire life of the interface. The addition of diamond-like carbon pads to the slider 36 allows a reduction in the height of asperities 44 while still providing good stiction and wear performance. Because a higher level of interference is tolerable when pads 46 are made from diamond-like carbon, it is desirable to provide reduced laser texturing in landing zone 40 rather than no laser texturing, because of the added margin against stiction and the significantly reduced susceptibility to disc curvature variation.
The present invention provides a technique which provides pads on the slider and asperities in the landing zone of the disc to provide the benefits of both configurations. The addition of the diamond-like carbon pads on the air bearing surface of the head allows a reduction in the height of the texturing in the landing zone while still maintaining good stiction performance. Further, the height of the pads on the slider can be reduced to thereby lower fly height, improve performance and increase recording density. The pads can be designed to wear until a steady state is reached. Further, wear will not occur on the slider or on the disc. The present invention allows an increased level of interference between the head and the disc because the contact occurs on diamond-like carbon pads. In one preferred embodiment, the laser texturing on the disc surface is designed to have a glide avalanche equal or below the fly height. The height of the pads located on the head are designed to normally clear the disc in the data zone (untextured region). With the above mentioned goals and knowing the performance of the air bearing, a laser bump height is selected, and the pad height and location are derived. For example,
fly height=0.5 μ:inches
media texturing=0.5 μ:inches
pad height=300 Å and the location of bumps are 10-12 mils from trailing edge. In one embodiment, the laser texturing on the disc surface is 60-90 Å in height, 4-6 μm in diameter, with spacing from 11×11 to 16×16 μm and the pads on the slider surface are about 20 μm in diameter, 250-300 Å in height, with the trailing row positioned based on flying clearance, spaced 60 to 80 μm center to center, with 40 to 60 total pads (FIG. 3). The trailing rows of pads on the slider may be at a lower height than the leading pads (100 to 200 Å) based on flying clearance. Other variations of pad diameter and count may also be employed (FIG. 4). In another embodiment, laser texturing height is 40-100 Å and diameter is 3-8 μm with spacing from 11×11 to 25×25 μm. A texturing on the disc has a density of 8500 1/mm2 to 1600 1/mm2. This can be formed by laser texturing the surface.
Although the present invention has been described with reference to preferred embodiments, workers skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the invention. In general, the pads may be placed along any protruding portion of the air bearing surface such as the side rails, a center rail, a center island, etc. In general, the present invention includes any size, shape, height, placing, configuration, density, etc. of the pads or texturing set forth herein. The texturing or the pads can be made in accordance with process as desired. The invention may be used with any type of transducing element including inductive, magnetoresistive, optical elements or others.
Boutaghou, Zine-Eddine, Gui, Jing, Rao, Mukund C., Angelo, James E., Tang, Huan, Murphy, James M., Riddering, Jason W., Harrison, Joshua C.
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